So you are actually looking for examples or something like: http://jdevadf.oracle.com/adf-richclient-demo/faces/components/skinningKeys/panelHeader.jspx ?
If so, I don't think there is anything simular/clear out there on the web.
But you can check these files:
amx.css : https://www.dropbox.com/s/8h2s5h9g0jdvfy6/amx.css
dvtm.css : https://www.dropbox.com/s/wxo85c47idzp0fo/dvtm.css

Indeed the documentation on the ADF Mobile skinning styleclasses is currently incomplete, something we hope to improve in a future release. As per user404's suggestion, you can reverse engineer the css styleclasses from those two css files.

I suppose you are looking more at UI customization. Presently there seems to be no formal way for this.

How we used to achieve this was by inspecting the DOM structure, we could get the style classes and style attributes associated with that particular component.

Once we know the style classes we can override that particular style class from amx.css in our custom css file with css style values we need. At many points we may have to use !important declaration with our custom style property to prevent it from being overridden.